One of the chief advantages touted by Adobe Systems Inc. for its e-book copy protection technology, called Adobe Digital Experience Protection Technology (ADEPT), is that consumers can buy e-books for one e-reader and freely transfer them to other such devices, as well as their Apple and Windows computers.

While that's possible with Amazon.com's Kindle, which uses its own file format and Digital Rights Management (DRM) scheme, it requires more hassle. And it's unclear whether it will be possible at all with e-books purchased for the iPad from Apple Inc.'s coming iBook store, due to Apple's reported plan to use its own FairPlay DRM.

But users say ADEPT fails to live up to Adobe's promise of interoperability between e-readers and e-book stores. For instance, e-books bought from Barnes & Noble, for now, work only on the nook e-reader -- not other popular e-readers such as the Sony Reader, even though both use Adobe's DRM.

Available as part of the Adobe Content Server 5 software to be released later this year, this 'social DRM' makes it easier for users to loan e-books to close friends and family.

The problem appears to be that all other e-readers use Adobe's current Content Server 4 software, which doesn't offer a password option and puts a hard cap of 12 devices for any particular e-book.

Adobe downplays issue

Adobe business development manager Nick Bogaty downplays the problem.

"There should be no issues for devices that have the most recent version of the Adobe Reader SDK [Software Development Kit]," he said Wednesday. Adobe is pushing e-book vendors and publishers not to create DRM islands as Amazon and Apple have, he said. "There are contractual obligations for interoperability between stores and devices -- that's the whole benefit of our platform."

But Mike McGuire, an analyst with Gartner Inc., says the "concerns" are valid.

"There are some incompatibilities," he said. This gives ammunition for Apple and Amazon.com to fire back at those who criticize them for not embracing Adobe's DRM or ePub, respectively, he said.

Paul Biba, editor of the e-book blog, TeleRead, goes further, arguing that the current complaints fulfill the predictions made earlier by critics that any DRM would inevitably create confusion and friction that could possibly stunt the e-book market.

"Everybody, except Amazon, is practically lying through their teeth by telling consumers that they are using the so-called 'standard' Epub format and how this is a great benefit to everybody. Hogwash!" Biba wrote earlier this week. "The whole thing is a fraud."